As a non-aqueous electrolyte secondary battery, a wound type battery is used. In this type battery, a battery element is formed by laminating and winding a positive electrode including a positive electrode active material layer on both surfaces of a positive electrode current collector and a negative electrode including a negative electrode active material layer on both surfaces of a negative electrode current collector with a separator interposed therebetween, and the battery element is housed in a battery can.
When a wound-type non-aqueous electrolyte secondary battery is crushed by pressure from the outside or a separator between a positive electrode and a negative electrode is broken or melted, and a short-circuit occurs between the positive electrode and the negative electrode in the battery, abnormal heat generation may occur.
In order to prevent such situations and to improve safety, PTL 1 discloses that a wound-type non-aqueous secondary battery is provided with a current collector opposing surface, in which a positive electrode current-collector-exposed portion and a negative electrode current-collector-exposed portion are allowed to face each other, on both ends of each of a positive electrode and a negative electrode. According to the disclosure, the positive electrode current-collector-exposed portion may be provided on one surface of the positive electrode current collector. However, when the positive electrode current-collector-exposed portion is provided on both surfaces, contact of metal with low resistance can be obtained more reliably.
Furthermore, PTL 2 discloses that it may be insufficient to provide a current collector opposing surface in which a positive electrode current-collector-exposed portion and a negative electrode current-collector-exposed portion are allowed to face each other on both ends of each of the positive electrode and the negative electrode Therefore, PTL2 discloses that the current collector opposing surface in which the positive electrode current-collector-exposed portion and the negative electrode current-collector-exposed portion are allowed to face each other is provided also in an intermediate part of winding.